I may misunderstand your problem, but I just have a configuration repository for various "hosts". There are a couple of settings I share between them, and then just specify the differences.

"Deploying" one is as simple as `nixos-rebuild switch --flake .#hostName`

These are all dev environments running at the same time. I wasn't sure if Nix had some kind of port mapping or proxy config for this sort of thing. I'm still partial to having containers as self-contained build artifacts, I just like to have options as dev environments go, and "Docker from Nix" looks like the best option so far. But it's a vast ecosystem, and there's plenty I might be missing.